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- Title
Belowground competitive suppression of seedling growth by grass in an African savanna.
- Authors
Cramer, Michael; Wakeling, Julia; Bond, William
- Abstract
Coexistence of N-fixing legumes and non-legume trees with grasses in African savannas results in intense competition between these life-forms. We hypothesised that belowground competition might induce different nutritional constraints in N- versus non-N-fixing species. A field (Hluhluwe-imFolozi nature reserve, South Africa) competition experiment with two N-fixing legume species ( Acacia burkei and Acacia karroo) and two non-N-fixing species ( Schotia brachypetala and Spirostachys africana) both with clipped grass and without grass was established. Plants were supplied with no fertilizer, or generous amounts of fertilizer (200 kg N ha, 100 kg PO ha, 7.1 kg KO ha) supplied as either 28-10 (N-K), P or a combination of these fertilizers (NPK). Regularly clipped grass suppressed growth (by more than 90 %) of both N- and non-N-fixing seedlings equally. Biomass accumulation of seedlings grown with grass and the grasses themselves responded positively to NK and/or NPK, but not P, although P-fertilization did have effects on foliar [N] and δN values of trees and grasses showing that plants accessed the fertilizer. Tree δN values and foliar [N] were also modified by NPK, demonstrating access to fertilizer. However, the ameliorative effects of NPK on grass competition-induced biomass suppression were only partial. This may be due to 'non-resource competition' (i.e. root gaps) imposed by dense grass roots. The fact that nutrients were able to partially ameliorate the effects of grass competition, however, indicates that such 'non-resource competition' may be partially overcome by even more generous supply of fertilizers.
- Subjects
SOUTH Africa; SAVANNAS; SEEDLINGS; BIOMASS; WOODY plants
- Publication
Plant Ecology, 2012, Vol 213, Issue 10, p1655
- ISSN
1385-0237
- Publication type
Article
- DOI
10.1007/s11258-012-0120-7